The fabrication of semiconductor devices on substrates typically requires the deposition of multiple metal, dielectric and semiconductor film layers on the surface of a substrate. The film layers are typically deposited onto the substrates in vacuum chambers. Certain processing operations require the deposition of film layers or the etching of a previously deposited film layer. During these processing steps, one must properly align and secure the substrate in the processing chamber in which the desired deposition or etch process is performed.
Typically, the substrate is supported in the chamber on a support member, commonly called a susceptor or pedestal. The substrate is placed on, and secured to, the upper surface of the support member prior to the deposition or etch process. In one process, metal may be deposited onto the backside of the substrate following processing of the front side of the substrate. During this type of processing, the substrate is supported on rest buttons which extend from the upper surface of the support member to reduce the surface area contact between the substrate and the support member. The rest buttons are sized and positioned to locate the substrate at a desired location in the chamber. To ensure proper processing of the substrate, the substrate must be properly aligned relative to the support member and a generally planar surface must be presented for receipt of a deposition layer. The position of the support member in the chamber is selected to provide a desired spacing and relative geometry between the generally planar surface of the substrate and portions of the process chamber. In a sputter deposition process, the position and alignment of the substrate is selected to present a planar surface of the substrate co-planar to the planar target surface and at a distance from the target which is selected to provide uniform thickness deposition on the substrate.
Substrates on which film layers are deposited may be extremely thin. Thin substrates tend to warp or take on a "potato chip" profile. When the substrate warps, it no longer presents a generally planar surface to receive deposition material. The warped surface of the substrate results in a non-co-planar relationship between the substrate and the target, and variable spacing therebetween. Consequently, in applications where substrates have become bowed, the substrates must be flattened before they are exposed to the deposition environment. Otherwise, nonuniform thickness deposition of the film layer may result.
Typically, a clamp ring is used to flatten warped substrates and secure substrates to the support member. However, care must be exercised when securing a substrate so that the substrate is not damaged by the clamp ring. Clamp rings must be positioned both laterally and vertically relative to the substrate to ensure that the substrates are not damaged under the weight of the clamp ring or by contact between a misaligned substrate and a clamp ring as the substrate contacts the clamp ring. Typically, clamp rings also function in wafer capturing or alignment on the support member. Wing members extend downwardly and outwardly from the clamp ring to funnel a substrate into alignment with the clamp ring and the support member. Consequently, vertical and lateral forces are applied to the substrate as the wing members achieve lateral alignment and the clamping portion simultaneously achieves vertical alignment of the substrate, clamp ring and pedestal as the clamp ring settles on the pedestal.
In various processing systems such as CVD, PVD, and etch processes, clamp rings also provide shielding to prevent unconfined material from depositing on the interior surfaces of the chamber. Shield arrangements have been devised to restrict the processing environment to a region adjacent to the surface of the substrate. The shield systems typically include a fixed wall portion which extends between the chamber cover and the position within the chamber where the pedestal is positioned during processing. The fixed wall portion extends around the circumference of the pedestal when the pedestal is positioned for processing, and thus blocks access of the processing environment to the walls and interior components of the chamber.
Presently, clamp ring assemblies for substrate shielding, positioning and clamping require that the substrate be positioned and clamped simultaneously. In the standard clamp ring configuration, the substrate is centered on the support member by the downwardly extending wing members of the clamp ring. These angled wings extending downwardly from the clamp ring capture the substrate and position the substrate laterally while at the same time clamping the substrate to the support member as the support member is moved upward through the clamp ring supported in the chamber. This leaves lateral alignment between the substrate and the support member to the last moment before the substrate is clamped to the support for processing. This places undue stress on the substrate because it is being aligned and clamped at the same time, thereby simultaneously applying forces in both the lateral and the vertical direction.
It would, therefore, be desirable to provide a substrate alignment member to properly align a substrate on a support member using gravity without the need for contact with the clamp ring to provide the alignment, and then secure the substrate in its properly aligned position on the support member with a clamp ring. This way, the substrate is aligned before the clamp ring contacts it. It would also be desirable to prevent contact between the clamp ring and the substrate alignment member and avoid causing shadowing of the substrate. Also, it would be desirable to provide clamp ring alignment pins to align and support the clamp ring over the substrate.